Occlusal block design for lateral locking

ABSTRACT

A first appliance and a second appliance comprise engagement surfaces that provide mandibular relocation forces and forces to limit lateral movement of the jaw, such as opposing inclined surfaces on opposite sides of the mouth. In some embodiments, engagement surfaces between oral appliances comprise a curvature difference, which allows engagement at differing angles and positions.

RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. § 119(e) of U.S.Provisional Patent Application No. 62/945,797, filed Dec. 9, 2019, andtitled “OCCLUSAL BLOCK DESIGN FOR LATERAL LOCKING,” which isincorporated, in its entirety, by this reference.

BACKGROUND

The present disclosure is generally related to the treatment ofmalocclusions with oral appliances, such as devices for mandibularrelocation and methods of use.

Dental treatments may involve procedures for repositioning misalignedteeth and changing bite configurations for improved cosmetic appearanceand/or dental function. Repositioning can be accomplished, for example,by applying controlled forces to one or more teeth over a period oftime.

As an example, orthodontic repositioning may be provided through adental process that uses positioning appliances for repositioning teeth.Such appliances may utilize a thin shell of material having resilientproperties, referred to as an “aligner,” that generally conforms to apatient's teeth and applies tooth repositions forces to incrementallyrepositions the patient's teeth.

Placement of such an appliance over the teeth may provide controlledforces in specific locations to gradually move the teeth into a newconfiguration. Repetition of this process with successive appliances inprogressive configurations can move the teeth through a series ofintermediate arrangements towards a final arrangement.

Such systems typically utilize materials that are light weight and/ortransparent to provide as a set of appliances that can be usedsequentially in stages such that as the teeth move in response to thetreatment, a new appliance for a new state of treatment of can beimplemented to further move the teeth without having to take a newimpression of the patient's teeth at every increment of tooth movementin order to make the successive appliance.

In various instances, teeth of a patient's upper jaw and teeth of thepatient's lower jaw may contact in an incorrect or suboptimal manner(e.g., crowding, crossbite, deep bite). A proper fit of the occlusalsurfaces of the teeth is helpful for proper biting and chewing, as wellas desirable for aesthetic appearance. Otherwise, premature wear of theteeth, undesirable flexion of the teeth, and/or undesirable forces ondental restorations may be experienced by the patient. For instance, aproper fit can be a function of the relative positions of teeth and themandible and maxilla, either of which may be retruded or protrudedrelative to the ideal position. The maxilla (e.g., the upper jaw) is abone that is fixed to the skull. The mandible (e.g., lower jaw) is abone that is attached to the skull by numerous muscles which guide itsmovement. The mandible articulates at its posterior upward extremitieswith the temporal bone to form the jaw joint. The jaw joint is a looselyconnected joint that accommodates the variety of movements of themandible relative to the maxilla during biting and chewing motions. Thenumerous muscles attaching the mandible to the skull control and powerthe complex movements involved in biting and chewing. Because thecondylar relationship affords some flexibility in the positioning of thejaw, the lower jaw can be intentionally repositioned in accordance withthe fit of the teeth, for instance, by using an oral appliance.

Prior approaches to mandibular repositioning can be less than ideal inat least some respects. For example, at least some of the prior devicesthat extend between teeth or to the sides of the teeth can be somewhatlarger and less comfortable for the patient than would be ideal. Forexample, oral appliances that rely on the jaws closing to reposition themandible may allow less than ideal jaw closure. Also, work in relationto the present disclosure suggests that the contacting surfaces of theprior oral appliances may less than ideally suited to accommodatevariability on the patient's mouth. The prior structures relied upon totransmit of forces between the upper and lower jaws to reposition themandible can provide somewhat indirect forces, which can be related toundesirable mandibular movement. Also, the manufacturing of at leastsome of the prior oral appliances for mandibular relocation can besomewhat more complex to design and manufacture than would be ideal.

In light of the above, improved mandibular relocation devices thatovercome at least some of the above limitations of the prior deviceswould be helpful.

SUMMARY

Embodiments of the present disclosure provide improved oral appliancesfor mandibular relocation with improved engagement that can allowimproved jaw closure, less undesirable jaw movement and decreasedcomplexity. In some embodiments, a first appliance and a secondappliance of a first stage of treatment comprise engagement surfacesthat provide mandibular relocation forces and forces to limit lateralmovement of the jaw, such as opposing inclined surfaces on oppositesides of the mouth. In some embodiments, engagement surfaces betweenoral appliances comprise a curvature difference, which allows engagementat differing angles and positions. The curvature difference can alsofacilitate the design and manufacturing of the oral appliances becausethe engagement surfaces can be brought into engagement at various angleswith respect to each other. In some embodiments, the engagement betweena first appliance and a second appliance occurs at a locus of engagementthat can vary across the engagement surfaces as the draws are drawntoward each other, which can provide a more continuous movement andchange in mandibular relocation forces as the jaws are drawn toward eachother. Also, the curvature difference can allow the engagementstructures to have decreased height within the mouth of the patient,which can provide more direct engagement between the upper and lowerjaws of a patient.

In some embodiments, the first appliance and the second appliancecomprise a plurality of replicated occlusal blocks, which can facilitatedesign of the oral appliances and manufacturing. The plurality ofreplicated occlusal blocks may comprise a curvature difference thatallows the replicated blocks to engagement with each other at variousangles to accommodate individual variability of the patient's mouth,such as variability associated with a Curve of Spee. In someembodiments, each of the plurality of replicated occlusal blockscomprises a curvature difference across the engagement surface, whichallows the blocks to engage each other when flipped in orientation. Theplurality of replicated occlusal blocks can be placed at a plurality oflocations on the appliances to engage each other, which can facilitatedesign and manufacturing at the plurality of locations.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the features, advantages and principles of thepresent disclosure will be obtained by reference to the followingdetailed description that sets forth illustrative embodiments, and theaccompanying drawings of which:

FIG. 1 shows an oral appliance and engagement structures, in accordancewith some embodiments;

FIG. 2A shows a pair of engagement structures associated with an upperdental appliance, in accordance with some embodiments;

FIG. 2B shows a pair of engagement structures associated with a lowerdental appliance, in accordance with some embodiments;

FIG. 2C shows a schematic representation of an example relativepositioning of the upper engagement structures and the lower engagementstructures, in accordance with some embodiments;

FIG. 3 shows pair of engagement structures for repositioning a mandibleand reducing lateral movement, in accordance with some embodiments;

FIG. 4A shows a pair of engagement structures for repositioning amandible with a gap formed between the teeth and the engagementstructure, in accordance with some embodiments;

FIG. 4B shows a pair of engagement structures for repositioning amandible with a curved engagement surface to allow the engagementstructure to follow the Curve of Spee while providing a locus ofengagement, in accordance with some embodiments;

FIG. 5 shows a pair of engagement structures associated with an upperappliance and a lower appliance, in accordance with some embodiments;

FIG. 6 shows a pair of engagement structures associated with an upperappliance and a lower appliance utilizing a keyed positioning system, inaccordance with some embodiments;

FIG. 7 shows an engagement structure having a geometry that allows it tobe located within any quadrant of a dentition, in accordance with someembodiments;

FIG. 8 shows a pair of engagement structures in an engaged position, inaccordance with some embodiments;

FIG. 9 shows an engagement structure with a retaining feature, inaccordance with some embodiments; and

FIG. 10 shows an engagement structure with a retaining feature, inaccordance with some embodiments;

FIG. 11 shows a locus of engagement, in accordance with someembodiments;

FIG. 12 shows a top view of an engagement structure, in accordance withsome embodiments;

FIG. 13 shows a cross-sectional view of an appliance comprising one ormore layers of thermoformed material over an occlusal block;

FIG. 14 shows a side view of a pair of engagement structures forrepositioning a mandible and reducing lateral movement, in accordancewith some embodiments;

FIG. 15 shows a top view of an engagement structure for repositioning amandible and reducing lateral movement, in accordance with someembodiments;

FIG. 16 shows a side of an engagement structure for repositioning amandible and reducing lateral movement, in accordance with someembodiments

FIG. 17 shows a side view of a pair of engagement structures forrepositioning a mandible and reducing lateral movement, in accordancewith some embodiments;

FIG. 18 shows a side view of an engagement structure for repositioning amandible and reducing lateral movement, in accordance with someembodiments;

FIG. 19 shows a side view of an engagement structure for repositioning amandible and reducing lateral movement, in accordance with someembodiments;

FIG. 20 shows a side view of an engagement structure for repositioning amandible and reducing lateral movement, in accordance with someembodiments;

FIG. 21 shows a side of an engagement structure for repositioning amandible and reducing lateral movement, in accordance with someembodiments; and

FIG. 22 shows an orthodontic aligner including engagement structures forrepositioning a mandible and reducing lateral movement, in accordancewith some embodiments.

DETAILED DESCRIPTION

The following detailed description provides a better understanding ofthe features and advantages of the inventions described in the presentdisclosure in accordance with the embodiments disclosed herein. Althoughthe detailed description includes many specific embodiments, these areprovided by way of example only and should not be construed as limitingthe scope of the inventions disclosed herein.

The methods, apparatus, oral appliances and occlusal blocks disclosedherein are well suited for combination with prior devices such asaligners to reposition teeth, for example the Invisalign™ systemcommercially available from Align Technology, Inc. For example, aplurality of appliances can be sequentially placed for tooth movement atdifferent incremental sequential stages of treatment and for mandibularrelocation either in combination with tooth movement stages or separatestages for mandibular relocation. Also, the presently disclosedengagement structures and occlusal blocks are well suited forincorporation into prior devices for mandibular relocation to providedecreased size and improved engagement. For example, the presentlydisclosed engagement structures can be combined with one or morefeatures of Precision Wings.

The presently disclosed methods and apparatus are well suited forcombination with prior approaches to manufacturing aligners, such aswith direct fabrication and overmolding such as thermoforming. Forexample, the presently disclosed occlusal blocks can be placed on apositive mold of the patient's dentition, and one or more polymericlayers of material thermoformed over the occlusal blocks. Also, theocclusal blocks are well suited for additive manufacturing such as 3Dprinting. The plurality of occlusal blocks as described herein can berepeatedly placed on a computer model of the patient's mouth tofacilitate design of mandibular relocation appliances. Also, therepeated placement and decreased size can decrease the amount ofadditive manufacturing material and decrease manufacturing time, forexample when the appliance is directly fabricated as a single part withthe thin polymeric shell and occlusal blocks together, or when theocclusal blocks are manufactured separately and thermoformed.

The present disclosure describes appliances and structures formandibular relocation, including treating class II malocclusions, classIII malocclusions, and sleep apnea correction. An oral appliance forinsertion into the mouth of a patient may comprise a plurality ofocclusal blocks and engagement structures for generating mandibularrelocation forces and positioning. The appliance may include teethreceiving cavities for fitting over the teeth of a patient, such as withan orthodontic aligner. A plurality of occlusal blocks is provided withthe appliance and promote mandibular relocation, such as by promotingmandibular advancement, retraction, lateral correction, or acombination.

The occlusal blocks cooperate to align the mandible with the maxillaaccording to a treatment profile. For example, a first occlusal blockcan be associated with an appliance coupled to upper teeth of a patient,and a second occlusal block can be associated with an appliance coupledto lower teeth of a patient. The first and second occlusal blocks may belocated to interfere with one another to maintain the mandible in adesired position, such as be interfering with retraction, advancement,or lateral movement of the mandible once the mandible is properlylocated.

The occlusal blocks may have engagement surfaces in which a firstocclusal block on a first appliance engages a second occlusal block on asecond appliance. The engagement surfaces apply forces on the mandibleto correct for class II malocclusions, class III malocclusions, or othertypes of misalignment of the mandible.

The occlusal blocks may have the same geometry and may be configured tobe installed in any portion of the mouth of a patient to provide thefeatures and benefits described herein. The appliances formed with theocclusal blocks may comprise engagement surfaces for contacting eachother with engagement surfaces similar to the surfaces of the occlusalblocks as described herein.

FIG. 1 shows an oral appliance 100 and one or more engagement structures110 carried by the appliance 100. The appliance 100 can be configured tofit over an entire dental arch 120. In other embodiments, the oralappliance may be designed to fit over some or all of the teeth in theupper or lower jaw. For example, the dental appliance 100 may be formedwith a plurality of teeth receiving cavities that allow the oralappliance 100 to securely fit onto the dental arch. The oral appliance100 can be fabricated from a polymeric shell, or formed from anothermaterial, and include a number of teeth receiving cavities shaped toreceive corresponding teeth. Aligners for positioning teeth arecommercially available from Align Technology.

The one or more engagement structures 110 can be place at any suitablelocation of the oral appliance 100, but according to some embodiments,corresponding pairs of engagement structures 110 are placed on theappliance 100 associated with the upper jaw of a patient and on anappliance associated with the lower jaw of a patient. In someembodiments, the corresponding pairs of engagement structures 110reposition the lower jaw relative to the upper jaw. For example, thelower jaw may be repositioned anteriorly (e.g., correcting forretrognathism), posteriorly (e.g., correcting for prognathism), orlaterally with respect to the upper jaw. Accordingly, the correspondingpairs of engagement structures can be used with an oral appliance toaddress class 1, class 2, or class 3 malocclusions in a patient.

The oral appliance comprises suitable materials for use with an oralappliance. The oral appliance may be made of any suitable material aswill be appreciated by one of ordinary skill in the art. In someembodiments, the engagement structures 110 may be formed into the oralappliance, such as by overmolding, for example. As an example, one ormore engagement structures 110 may formed by placing an occlusal blockas described herein on a positive mold of a patient's dentition, and anovermold material, which may be any of a number of suitable polymers, ismolded over the one or more engagement structures 110 and the positivemold. The result is an oral appliance 100 that comprises a plurality ofteeth receiving cavities and the one or more engagement structures 110with the occlusal blocks as described herein embedded within the oralappliance 100, for example.

While the description may refer to a first appliance and a secondappliance, it should be understood that referring to the appliances withthis nomenclature is not intended to indicate a position of theappliance within the mouth of a patient. For instance, a first appliancemay be configured to fit over the upper dental arch of a patient or maybe configured to fit over the lower dental arch of a patient. Similarly,reference to a first engagement structure, second engagement structure,third engagement structure, or fourth engagement structure does not, byitself, indicate a position within the mouth of a patient, or a locationon a particular oral appliance, unless specified.

FIGS. 2A, 2B and 2C illustrate cooperating pairs of engagementstructures associated with an upper dental appliance 100 a along anupper dental arch 120 a and a lower dental appliance 100 b along anlower dental arch 120 b, in accordance with some embodiments. The upperdental appliance 100 a defines a plurality of teeth cavities sized andshaped to fit over the teeth of a patient. A pair of engagementstructures 110 a may be shaped, embedded, attached, affixed, orotherwise carried by the upper dental appliance 100 a, and may compriseocclusal blocks as described herein. In some embodiments, the engagementstructures 110 a and corresponding occlusal blocks have a midline 104that divides the engagement structure into a left and a right side. Theengagement structures have an occlusal surface that faces generally awayfrom the dentition on which appliance is placed. When in use, theocclusal surface 116 a of an engagement structure associated with anupper appliance will be oriented generally toward the lower appliance.Similarly, the occlusal surface of an engagement structure associatedwith a lower appliance will typically face toward the engagementstructure of upper appliance when in use by a patient.

In some embodiments, the engagement structure 110 a and correspondingocclusal block have an engagement surface 112 a that is generallyinclined in relation to the occlusal surface. It should be appreciatedthat the engagement surface can be sized and shaped in many ways and maybe curved, contoured, shaped, or sloped, for example. In someembodiments, as illustrated in FIG. 2A, where the engagement structureis outfitted to an upper oral appliance for placement on maxillaryteeth, the engagement surface may face generally anteriorly (e.g.,toward the front of the mouth, where the incisors are located).

In some embodiments, such as is illustrated in FIG. 2B, where theengagement structure 110 b is associated with a lower oral appliance 100b for placement on mandibular teeth, the engagement surface 112 b mayface generally posteriorly. When arranged as illustrated in FIGS. 2A and2B, the engagement surfaces 112 a, 112 b may cooperate to aid withmandible relocation. For example, as illustrated, the first engagementstructure 110 a may be located on an upper appliance 100 a, as shown inFIG. 2A, while a second engagement structure 110 b may be located on alower appliance100 b, as shown in FIG. 2B. In use, where the appliances100 are fitted to the dentition of a patient, as the patient bites down,the lower jaw comes forward (e.g., mandible advancement), and theengagement surfaces 112 associated with engagement structures of theupper appliance and lower appliance touch one another and interfere toprovide mandibular relocation. In some embodiments, the mandible isurged toward more forward position, which helps in correcting anoverbite of the patient. In addition, the engagement surfaces may alsohelp to reduce lateral movement, e.g., side to side movement of thelower jaw, which can promote mandibular relocation.

In some embodiments, the engagement structures are positioned andoriented to promote the mandible in a more rearward position. That is,the engagement structures may assist with retracting the mandible toassist in correcting an underbite of the patient, for example.

FIG. 3 shows a schematic representation of an example relativepositioning of the upper engagement structures and the lower engagementstructures, in accordance with some embodiments. In some embodiments,the engagement structures can be positioned and configured to correctretrognathism, e.g., underbite, or may be positioned and configured tocorrect for prognathism, e.g. overbite. By way of example, theconfiguration will be described as promoting mandibular advancement,although the engagement structure can be interchanged to providemandibular retraction.

As shown, a pair of first engagement structures are associated with alower appliance and can be placed on a lower dentition of a patient. Apair of second engagement structures may be associated with an upperappliance and can be placed on an upper dentition of a patient. In use,once the upper appliance and lower appliance are placed onto thedentition of a patient, as the appliances are brought together, theengagement structures contact each other. As the mandible is advanced,the patient is able to bite down and bring the upper appliance and lowerappliance together. Once a patient bites down, the first engagementstructures and the second engagement structures reduce the ability ofthe mandible to retract from a forward position.

As shown, the first engagement structure has a midline that partitionsthe first engagement structure into a first side and a second side, e.g.a left side and a right side. In some embodiments, the first engagementsurface is inclined with respect to the midline at an angle. In someembodiments, this angle of inclination a is about 5 degrees, 10 degrees,15 degrees, 20 degrees, 30 degrees, 40 degrees, or 45 degrees, or withina range defined by any two of the preceding values. In some embodiments,the angle a is within the range from about 10 degrees to about 25degrees.

In some embodiments, the angle of inclination a provides support to helpposition the mandible in a forward position, and in addition, providessupport to limit lateral movement as the first engagement surfacecontacts the second engagement surface at a locus of engagement. Forexample, the left and right sides of the appliances may compriseopposing engagement structures so as to limit lateral jaw movement whileproviding mandibular advancement forces. For example, a first engagementstructure and a second engagement structure on first side of theappliances on a first side of the mouth may contact each other with acorresponding angle of inclination so as to generate first a lateralforce associated with a first mandibular advancement force. A firstengagement structure and a second engagement structure on a second sideof the appliances on a second side of the mouth may contact each otherwith a corresponding angle of inclination so as to generate a secondlateral force associated with a second mandibular advancement force. Insome embodiments, the first and second forces are oppositely orientedand can help to maintain the mandible in position and decrease lateralmovement so as to promote mandibular relocation.

FIG. 3 illustrates a pair of engagement structures 110 for repositioninga mandible and reducing lateral movement, which may be incorporated intoan upper appliance and a lower appliance as described herein. In theillustrated configuration, a first engagement structure 110 a isassociated with a mandible on a mandibular appliance and a secondengagement structure 110 b is associated with a maxilla on a maxillaryappliance. The first engagement structure has an occlusal portion 120and a buccal portion 118. The occlusal portion of the first engagementstructure 110 b located on an appliance as described herein so as to belocated generally adjacent the occlusal surface of a lower tooth orteeth when the appliance has been placed on the lower teeth. When theappliance has been placed on the lower teeth, the occlusal portion ofthe first engagement structure 110 a is located between the upperdentition and lower dentition. The buccal portion 118 is positionedadjacent the buccal surface of the tooth or teeth and is between theteeth and cheek, for example when located near a molar or premolartooth. Although reference is made to a buccal portion, the appliance maycomprise a lingual portion extending from the occlusal portion to alingual side of the patient's teeth.

The occlusal portion 120 and buccal portion 118 each define anengagement structure 110 comprising an engagement surface 112 that isconfigured to engage a corresponding engagement surface 112 on acooperating engagement structure 110, such as the second engagementstructure 110 a. The engagement surface may be as described herein, andmay be inclined with respect to a midline of the engagement structure.In some embodiments, the engagement surface is substantiallyperpendicular to the midline of the engagement structure and thelimitation on lateral movement may be provided solely by the buccalportion. As illustrated, the first engagement structure may beassociated with the mandible, that is, the first engagement structuremay be attached or embedded within a first appliance for placement onthe lower dentition and the buccal portion extends proximate to andengages the buccal surface of one or more teeth of the maxilla. Thesecond engagement structure may be associated with the maxilla, that is,the second engagement structure may be attached or embedded within asecond appliance for placement on the upper dentition and the buccalportion extends proximate to and engages the buccal surface of one ormore teeth of the mandible. In this configuration, lateral movement ofthe mandible relative to the maxilla is reduced.

FIG. 4A shows a pair of engagement structures 110 for repositioning amandible with a gap 130 formed between the teeth and the engagementstructure 110. A first occlusal block 111 a may be secured to a firstappliance 111 a for placement on the dentition of a patient. The firstocclusal block 111 a can be carried by the first oral appliance 100 afor placement on the teeth as described herein. The first appliance 100a can be coupled to the first occlusal block 111 a during appliancefabrication, such as by overmolding, e.g. thermoforming, the thin layerof appliance material onto the first occlusal block to form the firstengagement structure, for example. As can be seen in FIG. 4A, there maybe a gap 130 between the maxilla of a patient and the first engagementstructure 110 a. This may be related to, at least in part, by the shapeof the first engagement structure 110 a and the second engagementstructure 110 b. For example, with flat surfaces the engagement betweenthe surfaces is generally intended to provide contact along the flatsurfaces. This engagement between flat surfaces can be related toconstraints in the angle of the occlusal blocks with respect to eachother, such as when the occlusal surfaces of the teeth correspond to acurved surface.

During manufacturing of appliances, a first base can be provided on apositive mold of the first teeth and the first occlusal block receivedon the first base. The appliance can be overmolded, e.g. thermoformed,on the first positive mold, the first base and the first occlusal blockto form the first appliance. The first appliance is removed from thepositive mold and base with the first occlusal block attached thereto.When placed on the teeth of the patient, a gap 130 may extend betweenthe first appliance and the first occlusal block. The second appliancecan be similarly fabricated with a second positive mold, a second base,and a second occlusal block.

In at least some instances, the dentition exhibits a curvature in atleast two dimensions, such as along the occlusal surfaces such that theocclusal surfaces do not extend along an occlusal plane. For example,the upper dentition and lower dentition may follow a dental arch, and inaddition, one or more of these may be curved along the occlusal surfaceswith a curve known as the Curve of Spee 124 as illustrated in FIG. 4A.In some embodiments, the engagement structures will have a tendency toalign with one another, such as where they form a surface-to-surfacecontact along flat engagement surfaces. Although one or more of theocclusal blocks can be inclined with respect to the occlusal surfaces ofthe teeth, this can create a gap 130, for example between the upperengagement structure and the upper dentition as shown in FIG. 4A. Workin relation to the present disclosure suggests that reinforcementstructures can be provided on the appliance proximate the gap in orderto reinforce the appliance near the gap.

Work in relation to the present disclosure suggests that flat surfacecontact may impart forces onto the first and/or second engagementstructure that may bias one or more of the engagement structures awayfrom the dentition. This bias may be accounted for by altering thecontact surfaces of the engagement structures to reduce applied forcesthat tends to draw one or more of the engagement structures away fromthe dentition, this solution may rely on individually designedengagement structures for each application and for individual patients.For example, custom occlusal blocks can be manufactured as describedherein to fill the gap shown in FIG. 4A, so as to extend from theappliance to the occlusal surface of one or more teeth on which theappliance is to be placed so as to fill the gap.

FIG. 4B shows a pair of engagement structures for repositioning amandible with one or more curved engagement surfaces. According to someembodiments, providing one or more curved engagement surfaces allowsvariation in the angle of engagement between the engagement structuresand can allow the engagement structure to follow the Curve of Spee 124.This can allow the occlusal blocks111 to a placed in proximity to theunderlying one or more teeth. In some embodiments, the one or morecurved surfaces provide a locus of engagement 132 that reduces forces onthe engagement structures that may tend to bias the engagementstructures away from the dentition, for example. The one or more curvedsurfaces 134 may comprise a curved surface of a first occlusal block anda flat surface 136 of a second occlusal block that engage each other ata locus of engagement.

In some embodiments, the appliances worn by the patient are formed byovermolding, such as thermoforming. For example, the first appliance canbe manufactured by placing a first occlusal block on a first base on afirst positive mold of first teeth of a patient and thermoforming thethin polymeric layer of material over the first positive mold of theteeth, the first base and the first occlusal block. The first appliancecan be removed with the first occlusal block attached thereto andsubjected to additional manufacturing steps as described herein. Thesecond appliance can be similarly manufactured. The first and secondappliances can be placed on the first and second teeth to provideengagement as illustrated in FIG. 4B.

In some embodiments, the locus of engagement approximates a line ofcontact that extends between the first engagement structure and thesecond engagement structure. Depending on the material used for theocclusal block and appliance material such as thermoformed material, theengagement structures may deform in response to contact therebetween,which may alter the locus of engagement. The one or more curvedengagement surfaces can allow the engagement structures to slide withrespect to each other, such that the locus of engagement moves as thejaws are drawn together.

While the locus of engagement may approximate and extend along a line ofcontact, it should be appreciated that the locus of engagement maycomprise one or more of many shapes, such as rectangular, oval orbutterfly shaped. In some embodiments the locus of engagement is boundedby a rectangle having a high width to height aspect ratio, such as 3:1,5:1, 8:1, 10:1, or greater. In other words, the locus of engagement mayapproximate a rectangle having a width substantially greater than itsheight.

In embodiments in which one of a pair of engagement structures includesa curved engagement surface, it can be located depending on the oralgeometry of the patient. For example, in some patients, the Curve ofSpee 124 is generally convex, which may facilitate locating anengagement structure with a curved engagement surface on the maxilla. Insome cases, the Curve of Spee 124 may be concave, which may facilitatelocating an engagement block with curved engagement surface on themandible, for example. In some embodiments, a cooperating pair ofengagement structures (e.g., one associated with the maxilla, and oneassociated with the mandible), have different geometries. The differinggeometries may assist in proper placement. In some instances, a pair ofcooperating engagement structures have similar, or even identical,geometries. In some embodiments, the engagement surface of cooperatingengagement structures is different, such as is illustrated in FIG. 4B.

FIG. 5 shows a pair of engagement structures 110 associated with anupper appliance 100 a for a maxillary arch 109 and a lower appliance 100b for a mandibular arch 106, in accordance with some embodiments. Thefirst engagement structure 110 a may be associated with a firstappliance 100 a. In some embodiments, the first appliance 110 acomprises a first engagement structure 110 a, and the first engagementstructure 110 a comprises a first occlusal block 111 a and the layer ofappliance material covering the first occlusal block. In someembodiments, the second appliance 100 b comprises a second engagementstructure 110 b, and the second engagement structure 110 b comprises asecond occlusal block 111 b and the layer of appliance material coveringthe second occlusal block. For example, the engagement structure 110 aof the first appliance may comprise a portion of the appliance materialcovering the first occlusal block 111 a and the engagement structure ofthe second appliance 110 b may comprise a portion of the appliancematerial covering the second occlusal block 111 a, in which contact ofthe first and second appliance surfaces at the locus of engagement 132transmits forces to the underlying occlusal blocks 111 and teeth.

The first and second appliances 100 can be manufactured as describedherein. In some embodiments, the first base 136 a is located on apositive mold of one or more maxillary teeth of a patient, such as oneor more molars, premolars, or a combination, by any suitable method ortechnique. The first occlusal block 111 a may be coupled to the firstbase 136 a in any suitable way, such as by an interference fit, a keyand keyhole fit, a boss and pocket, or any other suitable type ofconnection. The second occlusal block 111 b may be similarly coupled tothe second base 136 a, for example.

The first and second engagement structures 110 may have different shapesand may have different engagement surfaces. In some embodiments, thefirst engagement structure 110 a has a first engagement surface 112 athat is contoured (e.g., curved, shaped, profiled, or something otherthan a flat surface). The second engagement structure 110 b has a secondengagement surface112 b that cooperates with the first engagementsurface to aid in mandibular alignment. The second engagement surface112 b may be substantially flat, or may be contoured and configured tocooperate with the first engagement surface. Where a curved surfacemeets a flat surface, the locus of engagement may approximate a line. Insome embodiments, the engagement structure comprises an occlusal blockembedded within the associated appliance, which may be formed of amaterial as described herein. Accordingly, as a first appliance contactsa second appliance, the appliances my elastically deform and modify thelocus of engagement, which may be dependent on the forces between theengagement structures. For example, as the force between the engagementstructures increases, the area of the locus of engagement may increaseas the corresponding appliances elastically deform in response to thecontact force. The occlusal blocks of each appliance can transmit forcesfrom the other appliance to one or more teeth in contact with eachocclusal block.

In some embodiments, configuring the engagement structures to have asmaller locus of engagement, such as one approximating a line, allowsone of more of the first or second engagement structure to be positionedcloser to the associated teeth. This allows the height of eachengagement structure to be reduced as well as reduces a possible gapbetween the engagement structure and the associated teeth, which canresult in improved force transmission between the jaws with a smallerheight structure on each of the occlusal blocks. In some embodiments,this may allow the jaws to be drawn closer together and may result inimproved patient comfort and experience.

FIG. 6 shows a pair of engagement structures 110 associated with anupper appliance and a lower appliance utilizing a keyed positioningsystem, in accordance with some embodiments. A first base 136 a may beattached to a positive mold of one or more maxillary teeth of a patient.The first key 138 a may comprise a boss, or a key, or other structurethat helps determine the location of first occlusal block andcorresponding a first engagement structure. For example, the first base136 a may be attached to a positive mold of a maxillary tooth throughany suitable attachment structure or method, such as depositionmanufacturing of the positive mold and first base together. The firstocclusal block comprising 110 a the first engagement structure mayinclude a pocket, a keyhole, or other structure that is configured tofit over a protruding portion of the first base. The first appliance canbe manufactured with thermoforming over the first positive mold of firstteeth, the first base and the first occlusal block as described herein.In some embodiments, this keyed positioning system ensures that thefirst engagement structure is appropriately positioned within the mouthof a patient in accordance with a mandibular relocation treatmentprofile. The first base 136 a may comprise an intrusion to receive aprotrusion extending from the first engagements structure, and any typeor arrangement of positioning system can be utilized to promote theproper positioning, location, and orientation of the first engagementstructure. For example, a protruding structure of the first occlusalblock received in the intrusion of the first based can removed prior toplacing the first appliance on one or more teeth of the patient.

The second occlusal block 111 b of the second engagement structure maycomprise a keyed positioning system that cooperates with a second base136 b that is affixed to a positive mold of one or more mandibular teethof a patient. In some embodiments, the keyed positioning system of thesecond engagement structure is different than the keyed positioningsystem of the first engagement structure to reduce the opportunity oflocating the first and second engagement structures in the incorrectplace.

FIG. 7 shows an engagement structure 110 comprising occlusal block 111having a shape profile geometry that can be used and repeated at aplurality of locations, so as to engage a similar occlusal block at eachof the plurality of locations. For example, the occlusal block 111 canbe located within any quadrant of a dentition. The occlusal block 111may comprise an engagement 112 surface that is contoured. In someembodiments, the engagement surface 112 extends to a first edge 140 theis generally flat (e.g., having a curvature of approximately zero) andto a second edge 142 that is generally convexly curved. The engagementsurface 112 may define a smooth transition between the flat first edge140 and the curved second edge 142. Thus, the engagement surface 112defines a first portion 144 on a first side of the midline 104 having afirst curvature that is different than a second curvature on a secondportion 146 of the engagement surface on a second side of the midline104.

The occlusal block may comprise a recess 148 such as a slot, channelgrove or other component of the key mechanism as described herein, suchas a keyway. The recess 148 can be located along the midline 104 of theocclusal block, for example.

An engagement surface 112 as shown in FIG. 7 allows a cooperating pairof occlusal block 111 comprising engagement structures 110 configured tohave a substantially identical engagement surface 112. In someembodiments, the plurality of occlusal blocks comprises a substantiallyidentical three-dimensional shape profile over the entire externalsurface of each of the plurality of occlusal blocks. In someembodiments, the engagement structures are used as a pair, the flat edgeof a first engagement structure engages the curved edge of the secondengagement structure, and likewise, the curved edge of the firstengagement structure engages the flat edge of the second engagementstructure.

FIG. 8 shows two cooperating engagement structures 110 as in FIG. 7 thatmeet at a locus of engagement, which approximates a line of engagement.As shown, the curved edge of a first engagement 110 a structure mateswith a flat edge 140 b of a second engagement structure 110 b. In someinstances, the engagement surfaces 112 are inclined with respect to amidline of the engagement structure. In other words, the engagementsurface may not be perpendicular to the midline of the engagementstructure, but is inclined at some angle, such as 10°, or 12°, or 15°,or 20° or more, or within a range defined by any two of the precedingvalues. In some instances, the angle of inclination is within a rangefrom 5° to 15°. The angle of inclination may be selected such thatlateral motion of the mandible relative to the maxilla is reduced bycontact between the first engagement structure and the second engagementstructure, for example with a pair of engagement structures located oneach side of the jaw with a plurality of appliances as described herein.

In some embodiments, the overall shape of the engagement structure isselected so that a plurality of occlusal blocks comprising a pluralityof engagement structures all having substantially the same shape can beused anywhere on the dentition to provide the advantages describedherein. For example, a plurality of engagement structures can bemanufactured on a plurality of appliances through any suitablemanufacturing technique, such as a thermoforming process, molding,machining, or some other technique. The plurality of occlusal blockscomprising a plurality of engagement structures may all be substantiallyidentical in size and shape and can be positioned on the dentition of apatient any suitable location within the mouth of the patient. Forinstance, engagement structures that share a substantially identicalshape may be positioned in the lower left quadrant, upper left quadrant,lower right quadrant, and upper right quadrant within the mouth of apatient to provide mandible relocation. The engagement structures may beoriented and rotated as desired to provide mandible relocation forces,as described herein.

The plurality of occlusal blocks may contain a structure such as a slot,recess or keyway 138 a, 138 b to aid in location of each of theengagement structures. In some cases, the keyway structure extends aportion of the way through the thickness of the occlusal blocks and aportion of the engagement structures. In some embodiments, the keywayextends such that the engagement structure can be rotated and flippedaround to be installed within any quadrant of the mouth of a patientwhile utilizing a singular geometry and three-dimensional externalsurface profile for the plurality of engagements structures used formandibular relocation of a patient.

As described herein, occlusal block generally comprises a structure ofmaterial that extends generally away from the occlusal surface of one ormore teeth. An engagement structure may comprise an engagement structureof an occlusal block or an oral appliance that extends away from theocclusal surface of a tooth of a patient so as to engage an opposingengagement structure. Accordingly, when appropriately positioned withinthe mouth of a patient, as a patient bites down, the engagementstructures engage each other to generate mandibular relocation forces.

In some embodiments, the occlusal blocks comprising engagementstructures are positioned on a positive mold corresponding to adentition, and a layer of thermoformed material is placed over theocclusal blocks to form an appliance comprising engagement structures asdescribed herein. The engagement structure may comprise the samematerial as the thermoformed material or a different material. In someembodiments, the thermoformed material comprises a polymeric material.The engagement structure may comprise a hardness that is similar ordifferent than the thermoformed material, (e.g., softer or harder).

FIG. 9 shows another view of the occlusal block 111 of FIGS. 7 and 8,which may comprise a retaining feature 152, in accordance with someembodiments. An occlusal block may comprise additional features, such asretention features so as to promote retention of the engagementstructure with a corresponding appliance. As illustrated, the occlusalblock 111 may comprise an engagement surface 112, an occlusal surface116, and one or more undercuts 152 on a side surface 150. The one ormore undercuts 152 may define a draft angle and be configured so thatthe undercut becomes greater or deeper toward the occlusal surface 160.Other retention features may be provided, such as protrusions, grooves,pockets, chamfers, draft angles, and the like to allow additionalmechanical connections between the occlusal block 111 and thethermoformed material of the appliance. The one or more retentionfeatures on the occlusal block 111 are well suited for use withthermoformed appliances comprising one or more layers of polymericmaterial as described herein, so as to promote retention of the occlusalblock 111 with the one or more layers of thermoformed material.

The undercut 152 may be formed on one or more side surfaces 150 of theengagement structure. During thermoforming, the thermoforming materialmay flow into the undercut 152 to provide a more secure assembly of theengagement structure within the appliance.

FIG. 10 shows another view of an engagement structure 110 comprising anocclusal block 110 with a retaining feature, such as undercut 152, as inFIG. 9, in accordance with some embodiments. The retaining feature maycomprise an undercut 152 formed by a draft 154 within the side surface150 of the engagement structure. The angle of the draft may be on theorder of or about 10° relative to the vertical axis of the engagementstructure, extending perpendicular to the occlusal surface 116. Otherangles are can be used, and the angle can be within a range from about1° to about 45° to provide the benefits of the retaining feature, forexample.

According to some embodiments, the occlusal block 111 is held in thethermoformed appliance 100 by the retaining feature and additionalchemical or mechanical fastening means are optional. In someembodiments, the retaining feature is sufficient to maintain theengagement structure within the appliance.

Additional fastening mechanisms can be used with, or without, theretaining feature, such as any of a variety of adhesives that promote achemical bond, a mechanical bond, or a combination. In some cases, theappliance is made by layering a thermoformed material over theengagement structure and the thermoformed material is able to flow in asoftened state to fill in the retaining feature to provide a mechanicalconnection between the engagement structure and the appliance.

The side surface of the engagement structure may additionally have adraft angle, such that the engagement structure, as a whole, is narrowerat its base and wider as it extends away from the tooth to provideadditional attachment security between the engagement structure and theappliance. The draft angle may be on the order of or about 10° and maybe any suitable angle within a range from about 1° to about 30°.

FIG. 11 shows an engagement structure 110 of a locus of engagement 134,in accordance with some embodiments. The occlusal block 111 may compriseany of the structures of the occlusal blocks referred to in FIGS. 6 to11. As described herein, where an engagement surface 112 of twocooperating engagement structures comprises one or more curved surfaces,the locus of engagement 134 may extend along a line. However, in someembodiments, the locus of engagement may approximate other shapesrelated to contact areas as described herein. As illustrated, the locusof engagement 134 may be wider near a center of the engagement surfaceand become thinner toward the sides of the engagement surface. The locusof engagement may comprise an external surface of an oral appliance incontact with an external surface of another appliance. Alternatively orin combination, the locus of engagement may comprise a force receivingsurface of the occlusal block through which engagement force istransmitted through one or more layers of polymeric material placed overthe occlusal block. In some embodiments, the locus of engagement of theocclusal block corresponds to surface contact areas of the engagementstructures on exterior surfaces of the appliances in contact with eachother.

In some embodiments, the locus of engagement may be substantiallyparallel with one or more surfaces of the engagement structure, such asthe occlusal surface. However, as illustrated, in some embodiments, thelocus of engagement is not parallel with the occlusal surface, and maybe tilted with respect to the occlusal surface, for example as a resultof varying or an asymmetric curvature of the engagement surface. Othershapes and sizes of a locus of engagement are contemplated and describedherein, and the locus of engagement may follow a curved line in one,two, or three dimensions. That is, the locus of engagement may follow acurved line when viewed from the top, the front, or the side ofcooperating engagement structures. Additionally, the locus of engagementmay comprise an area that is less than the area of the engagementsurface. For example, the locus of engagement may comprise about 10% ofthe area of the engagement surface. In some embodiments, the locus ofengagement may comprise less than about 10%, 20%, 30%, 40%, 50%, 60%,70%, or 80% of the area of the engagement surface. In some embodiments,the locus of engagement moves when the jaws are drawn toward each otherand the mandible protruded or retracted and the contact surfaces slidewith respect to each other. This movable locus of engagement can provideimproved comfort for the patient because the amount of force to themandible gradually increases as the jaws are drawn toward each other.

FIG. 12 shows a top view of an occlusal block 111 of an engagementstructure 110 according to some embodiments. The occlusal block 111 maycomprise any of the structure of the occlusal blocks of FIGS. 6 to 11.In some embodiments, the occlusal blocks of FIGS. 6 to 11 comprise thesame occlusal block as shown in FIG. 12. The occlusal block 111comprises an occlusal surface 116 and an engagement surface 112. Asurface 113 opposite the engagement surface 112 may be rounded, squared,or comprise some other shape. In some embodiments, the engagementsurface 112 comprises a curved profile, a flat profile or a varyingcurvature profile and combinations thereof. The engagement surface 112may comprise a plurality of profiles, such as a combination of a flatprofile 172, and one or more curved profiles 170. As illustrated, theengagement structure comprises a flatter profile 172 near one edge ofthe engagement surface, a curved profile 170 adjacent an opposite edgeof the engagement surface, and a smooth grated transition between theflatter profile 172 and the curved profile 170.

As illustrated, the engagement surface 112 may be wedge-shaped whenviewed from above. For example, the engagement surface may comprise anangle of inclination, 162, with respect to the midline 104. The angle ofinclination, 162 or a, may comprise an angle between a lateral lineextending along the engagement surface and a lateral line extendingperpendicular to the midline. The angle of inclination, a, can beconfigured to provide mandibular relocation forces and decrease lateralmovement as described herein, for example with reference to FIG. 2C.Each of the plurality of engagement structures may comprise an occlusalblock as shown in FIG. 12 for example. In some embodiments, the angle ofinclination, a, may be zero and the midline 104 of the engagementstructure may be tangent to the dental arch of the appliance at thelocation of the engagement structure on the appliance.

In some instances, the engagement surface may define a curve when viewedfrom the top. According to some embodiments, cooperating engagementstructures define engagement surfaces that are configured to cooperateto provide mandibular relocation forces as well as reducing lateralmovement of the mandible. According to some embodiments, the engagementsurfaces may be flat and define a surface to surface locus ofengagement.

Although FIGS. 2A to FIG. 12 show the occlusal blocks and associatedengagement structures in isolation, one of ordinary skill in the artwill readily recognize that this drawing also illustrates how theseblocks can be integrated into an oral appliance such as a thermoformedappliance. For example, the first block can be placed on a positive moldof the patient's dentition and thermoformed with a material as describedherein, such as a sheet of material. The thin sheet of material willthermoform over the occlusal block and positive mold of the patient'steeth. The surface contour of the thermoformed appliance will generallyconform to the external surface of the positive mold of the patient'steeth with the occlusal block placed thereon. The thermoformed appliancewith the occlusal blocks can be removed from the positive mold with theocclusal block attached to the appliance, and excess material removedfor placement on the patient's teeth. The upper appliance can besimilarly formed with a positive mold of the patient's upper teeth andthe second occlusal block. In some embodiments, the thin layer ofpolymeric material over the occlusal blocks comprises a shape contoursimilar to the shape contour of the occlusal blocks, and the thin layersof material on each appliance engage each other and transmit forcessimilarly to the forces described with respect to the occlusal blocks asdescribed herein.

In some embodiments, one or more of the coupled engagement surfaces maybe curved, and define a locus of engagement that is substantiallysmaller than the engagement surface area, for example so as to allowmovement of the locus of engagement. Also, the locus of engagementsmaller than the engagement surface area allows the engagement surfacesto engage each other with inclination with respect to the occlusalblocks, for example.

FIG. 13 shows a cross-sectional view of an appliance 100 comprising oneor more layers 102, 103, 106 of thermoformed material over an occlusalblock 111. The one or more layers 102, 103, 106 of thermoformed materialmay comprise a single layer of thermoformed material or a plurality oflayers of thermoformed material, for example. Although one occlusalblock is shown, each appliance may comprise a plurality of occlusalblocks as described herein, and a pair of appliances can be configuredto engage each other to generate mandibular relocation forces asdescribed herein. The one or more layers of thermoformed material maycomprise a first layer 102, a second layer 103 and a third layer 106, inwhich the one or more layers are shaped to the surface profile of theunderlying occlusal block. In some embodiments, the contacting surfacesof the engagement structures of the engaging appliances for mandibularrelocation substantially comprise the surface shape profile of theunderlying occlusal block as described herein.

In some embodiments, a first layer of thermoformed material on the firstocclusal block is shaped to form an external surface of a firstengagement structure of a first mandibular relocation appliance, andsecond layer of thermoformed material on the second occlusal block isshaped to form an external surface of a second engagement structure of asecond mandibular relocation appliance. The first block and the secondblock can be arranged to engage each other with the first layer and thesecond layer therebetween. The first layer and the second layer maycomprise a type of polymeric material and the first occlusal block andthe second occlusal block comprise the type of polymeric material, e.g.a co-polyester or a polyurethane.

In some embodiments, the one or more layers over the occlusal blockcomprises a plurality of layers. For example a first plurality of layersof thermoformed materials of the first appliance can cover the firstblock and a second plurality of layers thermoformed material of thesecond appliance of the second appliance can cover the second block. Thefirst plurality of layers may comprise a harder layer of materialbetween two softer layers of material and the second plurality of layersmay comprise the harder layer of material between the two softer layersof material. The harder layer may comprise a co-polyester and the softerlayers of material may comprise thermoplastic polyurethane, for example.For example, the first layer and third layers may comprise thermoplasticpolyurethane, the second layer may comprise co-polyester.

FIGS. 14-21 depict engagement structures 1411, 1511 that may share thefeatures and benefits of the engagement structures 110 discussed herein.

FIG. 14 shows a side view of a pair of engagement structures 1411, 1511for repositioning a mandible and reducing lateral movement. Theengagement structure 1410 may include an occlusal block 1411 with analigner portion over the occlusal block 1411. The tooth receivingcavities are omitted from FIG. 14 for clarity, however an alignerincluding the tooth receiving cavities and engagement structures isshown in FIG. 22. The occlusal block 1411 may include an engagementsurface 1430. In the embodiment shown in FIG. 14 the engagement surface1430 is a planar surface that faces an engagement surface of an opposingengagement structure, such as engagement structure 1510. The angle ofthe engagement surface 1430 with respect to the occlusal plane may matchthe angle of the engagement surface 1530 with respect to the occlusalplane. For example, the engagement surface 1430 may be parallel to theengagement surface 1530 when the appliances are worn by a patient. Aside 1421 of the occlusal block 1411 may include an upper or firstportion 1422 that is nearer the occlusal surface 1428 of the occlusalblock 1411 and a lower or second portion 1420 that is further from theocclusal surface 1428 of the occlusal block 1411, as compared to thefirst portion 1422. The lower portion 1420 may be shaped to form anundercut, such as undercut 152 discussed above. The undercut may definea draft angle and may be configured so that the lower portion 1420becomes wider toward the occlusal surface 1428. Other retention featuresmay be provided, such as protrusions, grooves, pockets, chamfers, draftangles, and the like to allow additional mechanical connections betweenthe occlusal block 1411 and the thermoformed material of the appliance1412. The one or more retention features on the occlusal block 1411 arewell suited for use with thermoformed appliances comprising one or morelayers of polymeric material as described herein. The draft anglespromote retention of the occlusal block 1411 with the aligner.

The undercut may be formed of the one or more side surfaces of theocclusal block. The undercut may be formed by the side surface having anangle of draft with respect to a vertical axis, such as a lineperpendicular to the occlusal surface or the occlusal plane of thealigner. The draft angle may about 5 degrees relative to the verticalaxis of the engagement structure, extending perpendicular to theocclusal surface. Other angles can be used, and the angle can be withina range from about 1 degree to about 45 degrees to provide the benefitsof the retaining feature, for example. In some embodiments, the draftangle may be between 1 degree at 10 degrees. More preferably betweenabout 3 degrees and about 7 degrees.

The side surface of the aligner material may additionally have a draftangle, such that the engagement structure, as a whole, is narrower at isbase and wider as it extends away from the tooth towards the upperportion 1422 in order to provide additional attachment security betweenthe engagement structure and the appliance. The draft angle may be about10 degrees and may be any suitable angle within a range from about 1degree to about 45 degrees. In some embodiments, the draft angle may beabout 5 degrees or between about 1 degree and about 10 degrees, morepreferably between about 8 degrees and about 12 degrees or between about3 degrees and about 7 degrees.

The upper portion 1422 may comprise a chamfer between the occlusalsurface 1428 and the lower portion 1420 of the occlusal block 1411. Thechamfer may be formed in or of a surface of the side 1421 of theocclusal block 1411. The chamfer may be formed of the one or more sidesurfaces of the other portion occlusal block. The chamfer may be formedby the side surface having an angle of chamfer with respect to avertical axis, such as a line perpendicular to the occlusal surface. Thechamfer angle may about 20 degrees relative to the vertical axis of theengagement structure, extending perpendicular to the occlusal surface oran occlusal plane of the aligner. Other angles are can be used, and theangle can be within a range from about 1 degree to about 45 degrees, forexample. In some embodiments, the chamfer angle may preferably bebetween about 15 degrees and about 25 degrees, more between about 18degrees and about 22 degrees.

The occlusal block 1411 may have a height 1412 that extends from a baseof the occlusal block to an occlusal surface 1428 of the occlusal block1411. The height of the occlusal block may be between 2 mm and 15 mm,more preferably between 3 mm and 12 mm, and most preferably between 5 mmand 7 mm, inclusive.

In some embodiments the occlusal block 1411 may have a height of 5 mm.In such an embodiment, the upper portion 1422 may have a height 1416 ofabout 2.5 mm extending from the occlusal surface 1428 to a locationwhere the chamfer of the upper portion 1422 meets the undercut of thelower portion 1420. In such an embodiment, the lower portion may have aheight 1418 of about 2.5 mm extending from a base of the occlusal block1411 to the location where the chamfer of the upper portion 1422 meetsthe undercut of the lower portion 1420.

In some embodiments, the height of the upper portion and the height ofthe lower portion are about 50% of the overall height 1412. In someembodiments the height of the lower portion and the height of the upperportion are between 20% and 80% of the overall height 1412 of theocclusal block 1411.

The side surface of the aligner material may additionally have a chamferangle, such that the engagement structure, as a whole, is narrower atits occlusal surface and wider as it extends away from the occlusalsurface towards the lower portion. The draft angle may be about 10° andmay be any suitable angle within a range from about 1° to about 45°.

The occlusal block 1411, and corresponding aligner 1412, may have anocclusal surface, such as occlusal surface 1428, that is substantiallyparallel to the occlusal plane of the patient's dentition or an occlusalplane of the aligner 1412. The occlusal block 1411 may include a backsurface 1424 that is opposite the engagement surface 1430. The backsurface may be formed at an angle 1426 with respect to the vertical axisof the engagement structure. The angle 1426 may be about 20 degreesrelative to the vertical axis of the engagement structure, extendingperpendicular to the occlusal surface. Other angles are can be used, andthe angle can be within a range from about 0 degrees to about 45degrees, for example. In some embodiments, the angle is between about 15degrees and about 25 degrees, more preferably between about 18 degreesand about 22 degrees.

In some embodiments, the occlusal block 1411 may include one or morealignment structures 1432 to aid in the alignment of the occlusal block1411 in the aligner shell 1412. The alignment structure 1432 may be anelongated keyway formed within a side 1421 of the occlusal block 1411.The alignment structure 1432 of the occlusal block may align in adirection perpendicular to the occlusal surface 1428 of the occlusalblock 1411. In some embodiments, the alignment structure 1432 alignswith a corresponding alignment structure on the aligner 1412. Forexample, the aligner may include a key shaped to match the keyway 1432.In some embodiments, an alignment structure may be an etching or othervisual indicator on the occlusal block 1411 that aligns with an etchingor visual indicator on the aligner 1412 when the occlusal block isproperly located within the aligner.

Similar to the engagement structure 1410, the engagement structure 1510may include an occlusal block 1511 with an aligner over the occlusalblock 1511. The engagement structure 1410 may be shaped and positionedon an aligner for placement on a lower arch of a patient, while theengagement structure 1510 is shaped and formed on an aligner forplacement on an upper arch of a patient. The engagement structure 1510may have similar features as engagement structure 1410. The occlusalblock 1511 may include an engagement surface 1530. In the embodimentshown in FIG. 14 the engagement surface 1530 is a planar surface thatfaces an engagement surface 1430 of an opposing engagement structure,such as engagement structure 1410. The angle of the engagement surface1530 with respect to the occlusal plane may match the angle of theengagement surface 1430 with respect to the occlusal plane. For example,the engagement surface 1430 may be parallel to the engagement surface1530 when the appliances are worn by a patient. A side 1521 of theocclusal block 1511 may be separated into an upper or first portion 1522that is nearer the occlusal surface 1528 of the occlusal block 1511 anda lower or second portion 1520 that is further from the occlusal surface1528 of the occlusal block 1511, as compared to the first portion 1522.The lower portion 1520, which may be more gingivally located than theupper portion, may be shaped to form an undercut, such as undercut 152discussed above. The undercut may define a draft angle and be configuredso that the undercut lower portion becomes wider toward the occlusalsurface 1528. Other retention features may be provided, such asprotrusions, grooves, pockets, chamfers, draft angles, and the like toallow additional mechanical connections between the occlusal block 1511and the thermoformed material of the appliance 1512. The one or moreretention features on the occlusal block 1511 are well suited for usewith thermoformed appliances comprising one or more layers of polymericmaterial as described herein, so as to promote retention of the occlusalblock 1511 with the one or more layers of thermoformed material.

The undercut may be formed of the one or more side surfaces of theocclusal block. The undercut may be formed by the side surface having anangle of draft with respect to a vertical axis, such as a lineperpendicular to the occlusal surface. The draft angle may about 5degrees relative to the vertical axis of the engagement structure,extending perpendicular to the occlusal surface. Other angles are can beused, and the angle can be within a range from about 1 degree to about45 degrees to provide the benefits of the retaining feature, forexample. In some embodiments, the draft angle may be between about 1degree and about 10 degrees, more preferably between about 3 degrees andabout 7 degrees. The side surface of the aligner material mayadditionally have a draft angle, such that the engagement structure, asa whole, is narrower at its base and wider as it extends away from thetooth towards the upper portion 1522 to provide additional attachmentsecurity between the engagement structure and the appliance. The draftangle may be about 5 degrees and may be any suitable angle within arange from about 1 degrees to about 45 degrees.

The upper portion 1522 may comprise a chamfer between the occlusalsurface 1428 and the lower portion 1520 of the occlusal block 1511. Thechamfer may be formed in a surface of the side 1521 of the occlusalblock 1511. The chamfer may be formed of the one or more side surfacesof the other portion occlusal block. The chamfer may be formed by theside surface having an angle of the chamfer with respect to a verticalaxis, such as a line perpendicular to the occlusal surface. The chamferangle may about 20 degrees relative to the vertical axis of theengagement structure, extending perpendicular to the occlusal surface.Other angles are can be used, and the angle can be within a range fromabout 1 degree to about 45 degrees, for example. In some embodiments,the angle is between about 15 degrees and about 25 degrees, morepreferably between about 18 degrees and about 22 degrees.

The occlusal block 1511 may have a height 1512 that extends from a baseof the occlusal block to an occlusal surface 1528 of the occlusal block1511. The height of the occlusal block may be between 2 mm and 15 mm,more preferably between 3 mm and 10 mm, and most preferably between 5 mmand 7 mm, inclusive.

In some embodiments, the occlusal block 1511 may have a height of 5 mm.In such an embodiment, the upper portion 1522 may have a height of about2.5 mm extending from the occlusal surface 1528 to a location where thechamfer of the upper portion 1522 meets the undercut of the lowerportion 1520. In such an embodiment, the lower portion may have a height1519 of about 2.5 mm extending from a base of the occlusal block 1511 tothe location where the chamfer of the upper portion 1522 meets theundercut of the lower portion 1520.

In some embodiments, the height of the upper portion and the height ofthe lower portion are about 50% of the overall height 1515. In someembodiments the height of the lower portion and the height of the upperportion are between 25% and 75% of the overall height 1515 of theocclusal block 1511.

The side surface of the aligner material may additionally have a chamferangle, such that the engagement structure, as a whole, is narrower atits occlusal surface and wider as it extends away from the occlusalsurface towards the lower portion. The draft angle may be about 5° andmay be any suitable angle within a range from about 1° to about 45°.

The occlusal block 1511, corresponding aligner 1512 may have an occlusalsurface 1528 that is at an angle 1529 with respect to the occlusal planeof the patient's dentition or an occlusal plane of the aligner 1512. Insome embodiments, the occlusal surface of the occlusal block 1511 is atan angle 1529 of between 3 degrees and 15 degrees with respect to theocclusal plan. Preferably the angle 1529 is between 5 degrees and 10degrees. In some embodiments, the angle matches the Curve of Spee of thepatient's dentition at the location of the engagement structure 1510.The occlusal surface may be angled with respect to the occlusal plane orto match the Curve of Spee in order to provide space between theocclusal surface of an opposing jaw. In some embodiments, the angleand/or the height of the occlusal block, such as a distal height of theblock, may be provided to form a gap or clearance from the toothsurfaces of the opposing jaw. For example, the occlusal surface may havea clearance during occlusion of the patients jaws of about 1 mm, 2 mm, 3mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, or 10 mm. In some embodiments,the clarence may be between about 1 mm and 10 mm, or between about 2 mmand about 5 mm.

The occlusal block 1511 may include a back surface 1524 that is oppositethe engagement surface 1530. The back surface may be formed at an anglewith respect to the vertical axis of the engagement structure. The anglemay be about 10 degrees relative to the vertical axis of the engagementstructure, extending perpendicular to the occlusal surface. Other anglesare can be used, and the angle can be within a range from about 1 degreeto about 45 degrees, for example. In some embodiments, the angle may bebetween about 5 degrees and about 15 degrees, more preferably betweenabout 8 degrees and about 12 degrees.

In some embodiments, the occlusal block 1511 may include one or morealignment structures 1532 to aid in the alignment of the occlusal block1511 in the aligner shell 1512. The alignment structure 1532 may be anelongated keyway formed within a side 1521 of the occlusal block 1511.The alignment structure 1532 of the occlusal block may align in adirection perpendicular to the occlusal surface 1528 of the occlusalblock 1511. In some embodiments, the alignment structure 1532 alignswith a corresponding alignment structure on the aligner 1512. Forexample, the aligner may include a key shaped to match the keyway 1532.In some embodiments and alignment structure may be an etching or othervisual indicator on the occlusal block 1511 that aligns with an etchingor visual indicator on the aligner 1512 when the occlusal block isproperly located within the aligner.

FIG. 15 shows a top view of an engagement structure 1410. As shown inFIG. 15 the occlusal block 1411 may include alignment structures 1432 onone or both of the buccal and lingual sides of the engagement structure.Although depicted as having a single alignment structure 1432 on each ofthe buccal and lingual sides of the engagement structure 1410, in someembodiments, the engagement structure may include one or more, more than1, more than 2, or 1, 2, 3, or 4 alignment structures on each side.Although depicted as having a similar cross-sectional shape such as acircular cross-sectional shape, in some embodiments, the alignmentstructures may have different shapes. For example, an alignmentstructure on a first side of the engagement structure may have circularcross-section while an alignment structure on a second side may have anoval. Other cross-sectional shapes for alignment structures includerectangular, triangular, an asymmetrical shapes. In some embodiments afirst alignment structure and assocaited key and keyways may be locatedin a more mesial position on the engagement structure while a secondalignment structure is located in a more distal position on theengagement structure.

The occlusal block 1411 may have a width 1413 that extends between amost buccal portion and a most lingual portion of the occlusal block.The width may be between 5 mm and 10 mm. In some embodiments, the baseand the occlusal surface of the occlusal block may also have widths. Thewidth of the base may be the same as the width of the occlusal surface.In some embodiments the width of the occlusal surface is less than thewidth of the base.

Although a lower engagement structure 1410 and corresponding featuresare depicted in FIG. 15, similar features and dimensions are applicableto other engagement structures such as an upper engagement structure1510.

FIG. 16 shows a side of an engagement structure 1410 from a rear viewlooking towards the back surface 1424 of the occlusal block. A side 1421of the occlusal block 1411 may be separated into an upper or firstportion 1422 that is nearer the occlusal surface 1428 of the occlusalblock 1411 and a lower or second portion 1420 that is further from theocclusal surface 1428 of the occlusal block 1411 as compared to thefirst portion 1422. The lower portion 1420 may be shaped to form anundercut. The undercut may define a draft angle 1602 and be configuredso that the undercut becomes wider toward the occlusal surface 1428. Thedraft angle may about 5 degrees relative to the vertical axis of theengagement structure, extending perpendicular to the occlusal surface.Other angles are can be used, and the angle can be within a range fromabout 1 degree to about 45 degrees to provide the benefits of theretaining feature, for example. In some embodiments, the draft angle maybe between about 1 degree and about 10 degrees, more preferably betweenabout 3 degrees and about 7 degrees.

The side surface of the aligner material may additionally have a draftangle, such that the engagement structure, as a whole, is narrower at isbase and wider as it extends away from the tooth towards the upperportion 1422 to provide additional attachment security between theengagement structure and the appliance. The draft angle may be about 10degrees and may be any suitable angle within a range from about 1degrees to about 45 degrees. Both the lingual side and a buccal side ofthe occlusal block may include an undercut on their respective lowersides. In some embodiments, the lower portion does not include an undercut or a draft angle.

The upper portion 1422 may comprise a chamfer between the occlusalsurface 1428 and the lower portion 1420 of the occlusal block 1411. Thechamfer may be formed in a surface of the side 1421 of the occlusalblock 1411. The chamfer may be formed of the one or more side surfacesof the other portion occlusal block. The chamfer may be formed by theside surface having an angle of the chamfer with respect to a verticalaxis, such as a line perpendicular to the occlusal surface. The chamferangle may about 20 degrees relative to the vertical axis of theengagement structure, extending perpendicular to the occlusal surface.Other angles are can be used, and the angle can be within a range fromabout 1 degree to about 45 degrees, for example both the lingual side inthe buccal side of the occlusal block may include a chamfer on theirrespective upper sides. In some embodiments, the upper portion does notinclude a chamfer or a chamfer angle.

FIG. 17 shows a side view of a pair of engagement structures. In someembodiments, the occlusal block 1411 may have a height of 7 mm. In suchan embodiment, the upper portion 1422 may have a height 1716 of about2.5 mm extending from the occlusal surface 1428 to a location where thechamfer of the upper portion 1422 meets the undercut of the lowerportion 1420. In such an embodiment, the lower portion may have a height1718 of about 4.5 mm extending from a base of the occlusal block 1411 tothe location where the chamfer of the upper portion 1422 meets theundercut of the lower portion 1420.

In some embodiments, the height of the upper portion and the height ofthe lower portion are about 50% of the overall height 1412. In someembodiments the height of the lower portion and the height of the upperportion are between 5% and 80% of the overall height 1412 of theocclusal block 1411, more preferably between about 20% and about 40%

In some embodiments, the occlusal block 1511 may have a height of 7 mm.In such an embodiment, the upper portion 1522 may have a height of about2.5 mm extending from the occlusal surface 1528 to a location where thechamfer of the upper portion 1522 meets the undercut of the lowerportion 1520. In such an embodiment, the lower portion may have a height1519 of about 4.5 mm extending from a base of the occlusal block 1511 tothe location where the chamfer of the upper portion 1522 meets theundercut of the lower portion 1520.

In some embodiments, the height of the upper portion and the height ofthe lower portion are about 50% of the overall height 1515. In someembodiments the height of the lower portion and the height of the upperportion are between 5% and 80% of the overall height 1515 of theocclusal block 1511, more preferably between about 20% and about 40%

FIG. 18 shows a side view of an engagement structure. The location ofthe occlusal block 1400 of the engagement structure 1410 within thealigner may be designed such that a lower surface 1434 of the occlusalblock 1411 sits at or above the most occlusal portion of the patient'sdentition. For example, the occlusal block 1411 shown in FIG. 18 isabove a cusp 1802 of the patient's tooth 1810. In some embodiments, thelocation of the occlusal block 1411 is such that the occlusal block doesnot interfere with the patient's dentition when the patient is notapplying jaw closing forces onto the engagement structures 1410. In someembodiments, the occlusal block may be located less than 0.10 mm abovethe occlusal surface of the patient's tooth 1810. In some embodiments,the occlusal block may be between 0 mm and 2 mm above the occlusalsurface of the patient's teeth. In some embodiments, the occlusal blockmay interfere with the patient's tooth. In some embodiments, theocclusal block may be located at a position such that it is less than0.1 mm below the occlusal surface of the patient's tooth 1810.

FIG. 19 shows a side view of an engagement structure for a lower arch.Occlusal block 1411 may have the length 1414. The length 1414 may besuch that the occlusal block spans a gap between two teeth in thepatient's dental arch that may be due to a missing or erupting tooth. Inthis way, the patient's teeth adjacent to the gap provide support forthe occlusal block 1411, such as when occlusal or repositioning forcesare applied to the block. In some embodiments, the length 1414 may bepatient specific such that the length 1414 of the occlusal block isbetween 0.5 and 6 mm longer than the width of the gap between the twononadjacent teeth 1910. For example, the occlusal block 1411 shown inFIG. 19 has a length to span the distance between the patient's firstpremolar and first molar caused by a missing second premolar. In someembodiments, the occlusal block 1411 may have a length to span thedistance between the patient's second premolar and second molar causedby a missing first molar. In some embodiments, the length of theocclusal block may be determined based on an average gap formed by themissing tooth. For example, for occlusal blocks on a lower arch thelength may be between 8 mm and 16 mm, more preferably between, 10 mm and14 mm. In some embodiments the length is about 12 mm.

FIG. 20 shows a side view of an engagement structure for an upper arch.Occlusal block 1511 may have the length 1514. The length 1514 may besuch that the occlusal block spans a gap between two teeth in thepatient's dental arch that may be due to a missing or erupting tooth. Inthis way, the patient's teeth adjacent to the gap provide support forthe occlusal block 1511, such as when occlusal or repositioning forcesare applied to the block. In some embodiments the length 1514 may bepatient specific such that the length 1514 of the occlusal block isbetween 0.5 and 6 mm longer than the width of the gap between the twononadjacent teeth 1910. For example, the occlusal block 1511 shown inFIG. 20 has a length to span the distance between the patient's firstpremolar and first molar caused by a missing second premolar. In someembodiments the occlusal block 1511 may have a length to span thedistance between the patient's second premolar and second molar causedby a missing first molar. In some embodiments, the length of theocclusal block may be determined based on an average gap formed by themissing tooth. For example, for occlusal blocks on an upper arch thelength may be between 6 mm and 16 mm, more preferably between, 8 mm and13 mm. In some embodiments the length is about 11 mm.

FIG. 21 shows a view from a distal location looking mesially towards arear surface of an engagement structure. The occlusal block 1511 mayhave a buckle-lingual width 2110 that is less than a width of thepatient's tooth over which the occlusal block is placed. The width beingmeasured between the buckle side of the tooth and the lingual side ofthe tooth. Development in connection with the present disclosure hasshown that an occlusal block or engagement structure with a width equalto greater than a width of the teeth over which the occlusal block isplaced because interference in the use of attachments such as attachment2112. The wide occlusal blocks act to inhibit engagement between theattachment 2112 and an orthodontic aligner. By using an occlusal block1511 with a width 2110 that is less than a width of the respectivetooth, attachments and other devices become more effective as comparedto wider occlusal blocks. Occlusal blocks 1411, 1511 they have a widthbetween 4 mm and 10 mm, more preferably between, 5 mm and 7 mm. in someembodiments the width is about 6 mm.

FIG. 22 shows an orthodontic aligner 2200 including engagementstructures 2210. The orthodontic aligner 2200 may be for an upper archor lower arch of a patient and may include two engagement structures2210 one on each of the right and left sides of the arch of the aligner.The orthodontic aligner may be one of a plurality of orthodonticaligners provided to the patient and warn successively in order toincrementally move the patient's teeth and adjust the position of themandible. The aligners may include tooth receiving cavities 2202 forincrementally repositioning patient's teeth. The aligner 2200 may alsoinclude one or more attachment receiving cavities 2204 for receiving anattachment placed on the patient's tooth. The engagement structures 2210may include an occlusal block received within a cavity formed by thealigner and extending from the occlusal portion of the aligner.

In some embodiments, the occlusal blocks for a set of aligners may beselected from a set of four occlusal block shapes and sizes. Forexample, the occlusal blocks may be selected from a set of occlusalblocks having a height of either about 5 mm or 7 mm. In someembodiments, the occlusal blocks for a right side of the lower arch andthe occlusal block for a left side of the same lower arch may have thesame size and shape while occlusal blocks for the left and right side ofan upper arch may have the same size and shape that is different thanthe size and shape of the lower occlusal blocks. In some embodiments theocclusal blocks for each of the stages of an incremental repositioningof a patient's mandible may be selected from a set of four occlusalblocks. The set of four occlusal blocks may include a lower occlusalblock having a first shape and a height of 5 mm, and lower occlusalblock having a second shape and a height of 7 mm, upper occlusal blockhaving third shape and a height of 5 mm, and fourth occlusal blockhaving fourth shape and a height of 7 mm. In some embodiments, theengagement surface of each of the four occlusal blocks may be at thesame angle with respect to the occlusal plane. In some embodiments, theangle of the occlusal surface of the upper occlusal blocks may be thesame.

While the occlusal blocks may comprise many suitable materials, in someembodiments, the first occlusal block and the second occlusal block eachcomprises a material softer than the harder layer. For example, thefirst occlusal block and the second occlusal block may comprise thesofter material of the first layer. Work in relation to the presentdisclosure suggests that occlusal blocks comprising a material similarto the layer of thermoformed material in contact with the occlusal blockcan improve bonding of the occlusal block to the appliance. For example,the first of the one or more layer may comprise polyurethane and theocclusal block may comprise polyurethane.

The occlusal blocks disclosed herein can be manufactured in many ways,for example with computer numeric control (CNC) machining, molding suchas injection molding and additive manufacturing. The presently disclosedengagement structures and appliances are well suited for additivemanufacturing. In some embodiments, the engagement structure andappliance can be directly manufactured with additive manufacturing as asingle integrated component. For example, the shaped engagementstructures as described herein can be directly fabricated with theappliance to form an integrated appliance, in which the occlusal blocksare directly fabricated with the polymer shell appliance as a singlepart, as will be appreciated by one of ordinary skill in the art.

Examples of suitable harder and softer materials suitable forcombination in accordance with embodiments of the present disclosure aredescribed in U.S. Pat. No. 9,655,693, entitled “Multilayer dentalappliances and related systems”, issued May 23, 2017, the entiredisclosure of which is incorporated herein by reference. The occlusalblocks may comprise any material disclosed herein, for example a hardmaterial or a soft material and may comprise a material similar to thematerial of the appliance or a material different from the material ofthe appliance.

In some embodiments, the hard polymer layer can be thicker than eitherof the soft polymer layers. The soft polymer layers can have the same ordifferent thicknesses. For example, the hard polymer layer can rangefrom a thickness of about 550 micrometers (“microns”) to about 750microns. The soft polymer layers can range from a thickness of about 25microns to about 100 microns. Multilayer sheets used for makingappliances having a hard polymer layer disposed between two soft polymerlayers can range from a thickness of about 600 microns to about 1000microns. In some embodiments, the thicknesses of the various layers canbe tailored for a particular stage of treatment for the patient.

Suitable polymeric materials for the hard polymer layer can include apolyester, a co-polyester, a polycarbonate, a thermoplasticpolyurethane, a polypropylene, a polyethylene, a polypropylene andpolyethylene copolymer, an acrylic, a cyclic block copolymer, apolyetheretherketone, a polyamide, a polyethylene terephthalate, apolybutylene terephthalate, a polyetherimide, a polyethersulfone, apolytrimethylene terephthalate or a combination thereof (e.g., a blendof at least two of the listed hard polymeric materials). In someembodiments, the hard polymer layer of the appliances can includepolymeric materials, such as a polycarbonate, a co-polyester, apolyester, and a thermoplastic polyurethane. In some embodiments, thehard layer can be composed of multiple hard layers, e.g., two or threehard polymer layers co-extruded to form one hard layer.

The hard polymer layer of the appliances of the present invention canhave a variety of physical properties that can, e.g., improve treatmentoptions for a practitioner. For example, physical properties such astensile strength, elongation at yield, elongation at break, tensilemodulus, flexural modulus, stress relaxation over time, and lighttransmission can each be specifically tailored for a particularapplication. In some embodiments, the hard polymer layer of theappliances can have a physical property of at least one of a tensilestrength at yield of between about 4000 pounds per square inch (psi) and6500 psi, an elongation at yield of greater than about 4%, an elongationat break of greater than about 70%, a tensile modulus of greater thanabout 150,000 psi, a flexural modulus greater than about 150,000 psi, astress relaxation at 24 hours testing in a wet environment (e.g.,between about 90%-100% relative humidity) is greater than 10%, and alight transmission between 400 nm and 800 nm of greater than about 75%.

Suitable polymeric materials for the soft polymer layers of theappliance can include a styrenic block copolymer (SBC), a siliconerubber, an elastomeric alloy, a thermoplastic elastomer (TPE), athermoplastic vulcanizate (TPV) elastomer, a polyurethane elastomer, ablock copolymer elastomer, a polyolefin blend elastomer, a thermoplasticco-polyester elastomer, a thermoplastic polyamide elastomer, or acombination thereof (e.g., a blend of at least two of the listed softpolymeric materials). The soft polymer layers can be the same materialor a different material. In certain embodiments, the first soft polymerlayer and the second soft polymer layer are the same polymeric material.

The soft polymer layers of the appliances can have a variety of physicalproperties. For example, physical properties such as hardness, ultimatetensile strength, elongation at break, tensile modulus, compression set,flexural modulus, and light transmission can each be specificallytailored for a particular application. In some embodiments, the softpolymer layers of the appliances can independently have a physicalproperty of at least one of a hardness within a range from about 60 A toabout 85 D, an ultimate tensile strength of greater than about 5000 psi,an elongation at break of greater than about 200%, a compression set atabout 70. degree. C. of greater than 40% after 24 hours, a flexuralmodulus of greater than about 35,000 psi, and a light transmissionbetween 400 nm and 800 nm of greater than about 75%.

As described herein, the layers of the appliances can include a hardpolymer layer disposed between two soft polymer layers. In oneembodiment, the multilayer appliances can include a hard polymer layerof one type of material (e.g., a co-polyester), and two soft polymerlayers of other types of material that can be the same or different(e.g., two soft polymer layers of thermoplastic polyurethane elastomer).In some embodiments, the multilayer appliances can also include a hardpolymer layer of at least two layers of polymer material. For example,the hard polymer layer can include several polymer layers laminatedtogether to form the hard polymer layer. The laminated hard polymerlayer can include at least two layers of any combination of thefollowing polymer materials: a polyester, a co-polyester, apolycarbonate, a thermoplastic polyurethane, a polypropylene, apolyethylene, a polypropylene and polyethylene copolymer, an acrylic, acyclic block copolymer, a polyetheretherketone, a polyamide, apolyethylene terephthalate, a polybutylene terephthalate, apolyetherimide, a polyethersulfone, and a polytrimethyleneterephthalate. Similarly, in some embodiments, the multilayer appliancescan include a soft polymer layer of at least two layers of polymermaterial. For example, the soft polymer layers can include a layer ofseveral polymer layers, laminated together. The laminated soft polymerlayers can include at least two layers of any combination of thefollowing polymer materials: a styrenic block copolymer (SBC), asilicone rubber, an elastomeric alloy, a thermoplastic elastomer (TPE),a thermoplastic vulcanizate (TPV) elastomer, a polyurethane elastomer, ablock copolymer elastomer, a polyolefin blend elastomer, a thermoplasticco-polyester elastomer, and a thermoplastic polyamide elastomer.

The tooth positioning appliances can be fabricated using a variety ofmethods. For example, methods for making the appliances can includethermoforming a multilayer sheet into an aligner by heating the sheetand then molding the sheet to a particular configuration. Exemplarymethods for fabricating the appliances, including those utilized in theInvisalign™. System, are described in numerous patents and patentapplications assigned to Align Technology, Inc. including, for example,in U.S. Pat. No. 9,103,338, entitled “Methods and systems thermoformingan object, issued on Aug. 18, 2015, as well as on the company's website,which is accessible on the World Wide Web (see, e.g., the url“invisalign.com”).

Unless otherwise noted, the terms “connected to” and “coupled to” (andtheir derivatives), as used in the specification and claims, are to beconstrued as permitting both direct and indirect (i.e., via otherelements or components) connection. In addition, the terms “a” or “an,”as used in the specification and claims, are to be construed as meaning“at least one of” Finally, for ease of use, the terms “including” and“having” (and their derivatives), as used in the specification andclaims, are interchangeable with and shall have the same meaning as theword “comprising”.

It will be understood that although the terms “first,” “second,”“third”, etc. may be used herein to describe various layers, elements,components, regions or sections without referring to any particularorder or sequence of events. These terms are merely used to distinguishone layer, element, component, region or section from another layer,element, component, region or section. A first layer, element,component, region or section as described herein could be referred to asa second layer, element, component, region or section without departingfrom the teachings of the present disclosure.

As used herein, the term “or” is used inclusively to refer items in thealternative and in combination, unless indicated otherwise.

As used herein, characters such as numerals refer to like elements.

The present disclosure includes the following numbered clauses.

Clause 1. A plurality of occlusal blocks for a mandibular relocation,comprising: a first occlusal block comprising a first surface; and asecond occlusal block comprising a second surface to engage the firstsurface; wherein the first surface and the second surface are shaped toengage each other with a curvature difference.

Clause 2. The plurality of occlusal blocks of clause 1, wherein thefirst surface and the second surface comprise similar shape profilesoriented in opposing directions.

Clause 3. The plurality of occlusal blocks of clause 1, wherein thefirst surface and the second surface are shaped to engage each otheralong an engagement line.

Clause 4. The plurality of occlusal blocks of clause 3, wherein thefirst surface and the second surface are shaped to engage each otherwith the curvature difference along a substantially straight line.

Clause 5. The plurality of occlusal blocks of clause 3, wherein thefirst surface and the second surface are shaped to engage each other ata locus of engagement, the locus of engagement extending along the line.

Clause 6. The plurality of occlusal blocks of clause 1, wherein thefirst occlusal block comprises a first midline and the first surfacecomprises a first portion on a first side of the midline and a secondportion on a second side of a midline, the first portion comprising acurvature different from the second portion.

Clause 7. The plurality of occlusal blocks of clause 6, wherein thesecond occlusal block comprises a second midline and the second surfacecomprises a first portion on a first side of the second midline and asecond portion on a second side of the second midline, the first portioncomprising a curvature different from the second portion.

Clause 8. The plurality of occlusal blocks of clause 7, wherein thefirst portion of the first surface comprises a curvature correspondingto a curvature of the second portion of the second surface and acurvature of the second portion of the first surface comprises acurvature corresponding to a curvature of the first portion of thesecond surface.

Clause 9. The plurality of occlusal blocks of clause 8, wherein each ofthe first portion and the second portion of the first surface and thefirst portion and the second portion of the second surface compriseconvex surfaces.

Clause 10. The plurality of occlusal blocks of clause 8, wherein thecurvature of the first portion of the first surface matches thecurvature of the second portion of the second surface and the curvatureof the second portion of the first surface matches the curvature of thefirst portion of the second surface.

Clause 11. The plurality of occlusal blocks of clause 8, wherein one ormore of the first portion or the second portion of the first surfacecomprises a curvature of zero and wherein one or more of the firstportion or the second portion of the second surface comprises acurvature of zero.

Clause 12. The plurality of occlusal blocks of clause 1, wherein a first3D shape profile of the first surface and a second 3D shape profile ofthe second surface correspond to each other and optionally wherein thefirst 3D shape profile matches the second 3D shape profile.

Clause 13. The plurality of occlusal blocks of clause 1, wherein thefirst occlusal block and the second occlusal block correspond toreplicas of each other.

Clause 14. The plurality of occlusal blocks of clause 13, wherein thefirst occlusal block comprises a first 3D exterior surface shape profileand the second occlusal block comprises a second 3D exterior surfaceshape profile and wherein the first 3D exterior surface shape profilematches the second 3D exterior surface shape profile to within 90% andoptionally wherein the first occlusal block comprises a first volume andthe second occlusal block comprises a second volume matching the firstvolume to within 90%.

Clause 15. The plurality of occlusal blocks of clause 1, comprising afirst layer of thermoformed material on the first occlusal block toshape a first engagement structure of a first mandibular relocationappliance and second layer of thermoformed material on the secondocclusal block to shape a second engagement structure of a secondmandibular relocation appliance.

Clause 16. The plurality of occlusal blocks of clause 15, wherein thefirst block and the second block are arranged to engage each other withthe first layer and the second layer therebetween.

Clause 17. The plurality of occlusal blocks of clause 16, wherein thefirst layer and the second layer comprise a type of polymeric materialand the first occlusal block and the second occlusal block comprise thetype of polymeric material.

Clause 18. The plurality of occlusal blocks of clause 15, comprising afirst plurality of layers of thermoformed materials of the firstappliance on the first block and a second plurality of layersthermoformed material of the second appliance of the second appliance onthe second block.

Clause 19. The plurality of occlusal blocks of clause 18, wherein thefirst plurality of layers comprises a harder layer of material betweentwo softer layers of material and the second plurality of layerscomprises the harder layer of material between the two softer layers ofmaterial, and optionally wherein the harder layer comprises aco-polyester and the softer layers of material comprise thermoplasticpolyurethane.

Clause 20. The plurality of occlusal blocks of clause 19, wherein thefirst occlusal block and the second occlusal block each comprises amaterial softer than the harder layer.

Clause 21. An apparatus for a mandibular relocation, comprising: a firstappliance comprising a first engagement structure, the first engagementstructure comprising a first engagement surface facing generallyanteriorly and inclined with respect to a first midline of the firstengagement structure; and a second appliance comprising a secondengagement structure, the second engagement structure comprising asecond engagement surface facing generally posteriorly and inclined withrespect to a midline of the second engagement structure; wherein one ormore of the first engagement surface or the second engagement surface iscurved to create an engagement line in a lingual-buccal direction withengagement between the first engagement surface and the secondengagement surface.

Clause 22. The apparatus of clause 21, further comprising the pluralityof occlusal blocks of any one of clauses 1 to 20.

Clause 23. An apparatus for mandibular relocation comprising: a firstappliance comprising, a first plurality of a teeth receiving cavities, afirst engagement structure comprising a first engagement surface, and asecond engagement structure comprising a second engagement surface; anda second appliance comprising, a second plurality of teeth receivingcavities, a third engagement structure comprising a third engagementsurface to engage the first engagement surface, and a fourth engagementstructure comprising a fourth engagement surface to engage the secondengagement surface; wherein the first and second engagement surfaces areinclined with respect to the third and fourth engagement surfaces,respectively, to generate mandibular relocation forces and limit alateral movement of the mandible.

Clause 24. The apparatus of clause 23, further comprising the pluralityof occlusal blocks of any one of clauses 1 to 20, and wherein the firstengagement structure comprises the first occlusal block and the thirdengagement structure comprises the second occlusal block.

Clause 25. The apparatus of clause 24, further comprising a thirdocclusal block corresponding to the first occlusal block and a fourthocclusal block corresponding the second occlusal block and wherein thesecond engagement structure comprises the third occlusal block and thefourth engagement structure comprises the fourth occlusal block.

Clause 26. The apparatus of clause 23, wherein the first engagementsurface is inclined relative to a midline of the first engagementstructure and the second engagement surface is opposingly inclinedrelative to a midline of the second engagement structure to limit thelateral movement of the mandible and reposition the mandible.

Clause 27. The apparatus of clause 23, wherein the third engagementsurface is inclined relative to a midline of the third engagementstructure and the fourth engagement surface is opposingly inclinedrelative to a midline of the fourth engagement structure to limitlateral movement of the mandible and reposition the mandible.

Clause 28. The apparatus of clause 23, wherein the first and secondengagement surfaces face generally anteriorly and wherein the third andfourth engagement surfaces face generally posteriorly to engage thefirst and second engagement surfaces to generate the mandibularrelocation forces.

Clause 29. The apparatus of clause 23, wherein the first and secondengagement surfaces face generally posteriorly and wherein the third andfourth engagement surfaces face generally anteriorly to engage the firstand second engagement surfaces to generate the mandibular relocationforces.

Clause 30. The apparatus of clause 23, wherein one or more of the firstengagement structure, the second engagement structure, the thirdengagement structure or the fourth engagement structure extends from anocclusal surface of one or more of the first appliance or the secondappliance and optionally wherein the one or more of the first engagementsurface, the second engagement surface, the third engagement surface orthe fourth engagement surface is located between occlusal surfaces ofthe first appliance and the second appliance.

Clause 31. The apparatus of clause 23, wherein one or more of the firstengagement surface or the third engagement surface comprises a curvedsurface to create a first locus of engagement and wherein one or more ofthe second engagement surface or the fourth engagement surface comprisesa curved surface to create a second locus of engagement.

Clause 32. The apparatus of clause 31, wherein the curved surfaceprovides engagement between the first engagement surface and the thirdengagement surface to accommodate a curve of Spee of a mouth andoptionally wherein a location of the locus of engagement changes withsubsequent appliances in response to changes of the curve of Spee.

Clause 33. The apparatus of clause 31, wherein the first engagementsurface and the third engagement surface are shaped to contact eachother at the first locus of engagement and provide a sliding locus ofengagement between the first engagement surface and the third engagementsurface to generate the mandibular relocation forces and limit lateralmovement.

Clause 34. The apparatus of clause 31, wherein the second engagementsurface and the fourth engagement surface are shaped to contact eachother at the second locus of engagement and provide sliding locus ofengagement between the second engagement surface and the fourthengagement surface to generate the mandibular relocation forces andlimit lateral movement.

Clause 35. The apparatus of clause 31, wherein the first locusengagement comprises a first engagement area that is less than one ormore of a first surface area of the first engagement surface or a secondsurface area of the second engagement surface and wherein the secondlocus engagement comprises a second engagement area that is less thanone or more of a third surface area of the third engagement surface or afourth surface area of the fourth engagement surface.

Clause 36. The apparatus of clause 35, wherein the first engagement areacomprises a contact area between the first engagement surface and thesecond engagement surface and the second engagement area comprises acontact area between the third engagement surface and the fourthengagement surface.

Clause 37. The apparatus of clause 23, wherein the mandibular relocationforces comprise mandibular advancement forces.

Clause 38. The apparatus of clause 23, wherein the mandibular relocationforces comprise mandibular retraction forces.

Clause 39. The apparatus of clause any one of the preceding clauses,wherein one or more of a first appliance or a second appliance comprisesa polymeric shell appliance.

Clause 40. A method, the method comprising using the plurality ofocclusal blocks or the appliance of any one of the preceding clauses.

Clause 41. A plurality of occlusal blocks for a mandibular relocation,comprising: a first occlusal block comprising a first engagement surfaceand a first side surface; a first keyway formed in the first sidesurface of the first occlusal block; a second occlusal block comprisinga second engagement surface to engage the first engagement surface and asecond side surface; and a second keyway formed in the second sidesurface of the first occlusal block.

Clause 42. The plurality of occlusal blocks of clause 41, wherein thefirst side surface has a lower portion and an upper portion.

Clause 43. The plurality of occlusal blocks of clause 42, wherein thelower portion extends from a base towards an occlusal surface.

Clause 44. The plurality of occlusal blocks of clause 43, wherein theupper portion extends from the occlusal surface towards the base.

Clause 45. The plurality of occlusal blocks of clause 44, wherein theupper portion meets the lower portion along a mesial-distal line betweenthe occlusal surface and the base.

Clause 46. The plurality of occlusal blocks of clause 45, the first sidesurface of the lower portion extends from the base towards the upperportion at a draft angle with respect to a line perpendicular to theocclusal plane.

Clause 47. The plurality of occlusal blocks of clause 46, wherein thefirst side surface is a buccal side surface and the first occlusal blockincludes a lingual side surface, opposite the buccal side surface, thelingual side surface extending from the base at the draft angle.

Clause 48. The plurality of occlusal blocks of clause 47, wherein thedraft angle is between 1 degree and 10 degrees.

Clause 49. The plurality of occlusal blocks of clause 47, wherein thedraft angle is about 5 degrees.

Clause 50. The plurality of occlusal blocks of clause 45, the first sidesurface of the upper portion defines a chamfer that extends from theocclusal surface towards the lower portion at an angle with respect to aline perpendicular to the occlusal plane.

Clause 51. The plurality of occlusal blocks of clause 46, wherein thefirst side surface is a buccal side surface and the first occlusal blockincludes a lingual side surface, opposite the buccal side surface, theupper portion of the lingual side surface defining a chamfer extendingfrom the occlusal surface at the angle.

Clause 52. The plurality of occlusal blocks of clause 50, wherein theangle is between 15 degrees and 25 degrees.

Clause 53. The plurality of occlusal blocks of clause 50, wherein theangle is about 20 degrees.

Clause 54. The plurality of occlusal blocks of clause 41, wherein theocclusal blocks have a height of about 5 mm.

Clause 55. The plurality of occlusal blocks of clause 41, wherein theocclusal blocks have a height of about 7 mm.

Clause 56. The plurality of occlusal blocks of clause 41, wherein thefirst occlusal block includes an occlusal surface, the occlusal surfacebeing parallel to an occlusal plane of the dentition of the patient.

Clause 57. The plurality of occlusal blocks of clause 41, wherein thesecond occlusal block includes an occlusal surface, the occlusal surfacebeing at an angle with respect to the occlusal plane, the angle beingbetween about 15 degrees and about 25 degrees.

Clause 58. The plurality of occlusal blocks of clause 57, wherein theangle being between about 3 degrees and about 15 degrees.

Clause 59. The plurality of occlusal blocks of clause 57, wherein beingbetween about 5 degrees and about 10 degrees.

Clause 60. The plurality of occlusal blocks of clause 57, wherein theangle is corresponds to the angle of the curve of Spee at the locationof the occlusal block.

Clause 61. The plurality of occlusal blocks of clause 41, wherein a baseof the occlusal block has a length, the length extending form a mesialmost edge to a distal most edge of the base, the length being between 8mm and 16 mm.

Clause 62. The plurality of occlusal blocks of clause 61, wherein thelength is between 10 mm and 14 mm.

Clause 63. The plurality of occlusal blocks of clause 61, wherein thelength is about 14 mm.

Clause 64. The plurality of occlusal blocks of clause 41, wherein a baseof the occlusal block has a width, the width extending form a buccalmost edge to a lingual most edge of the base, the width being between 4mm and 10 mm.

Clause 65. The plurality of occlusal blocks of clause 61, wherein thewidth is between 5 mm and 7 mm.

Clause 66. The plurality of occlusal blocks of clause 61, wherein thewidth is about 6 mm.

Clause 67. A system comprising: a plurality of orthodontic aligners,each of the plurality of orthodontic aligners having: tooth receivingcavities for incrementally repositioning a patient's teeth from aninitial position towards a final position; and engagement structures forincrementally repositioning a patient's mandible and comprising occlusalblocks of any one of clauses 1-66.

Clause 68. The system of clause 67, wherein a height of the occlusalblocks for each of the plurality of orthodontic aligners is about 5 mmor about 7 mm.

Clause 69. The system of clause 67, wherein a shape of each of theocclusal blocks for each aligner of the plurally of aligners for a lowerarch are the same shape.

Clause 70. The system of clause 67, wherein a shape of each of theocclusal blocks for each aligner of the plurally of aligners for anupper arch are the same shape.

Clause 71. An orthodontic treatment system comprising:

a plurality of sets orthodontic aligners, each of the plurality oforthodontic aligners having: a first plurality of a teeth receivingcavities, a first engagement structure comprising a first engagementsurface, and a second engagement structure comprising a secondengagement surface; and a second appliance comprising: a secondplurality of teeth receiving cavities, a third engagement structurecomprising a third engagement surface to engage the first engagementsurface, and a fourth engagement structure comprising a fourthengagement surface to engage the second engagement surface, and whereinthe first and second engagement surfaces are inclined with respect tothe third and fourth engagement surfaces, respectively, to generatemandibular relocation forces and limit a lateral movement of themandible.

Clause 72. The apparatus of clause 71, further comprising the pluralityof occlusal blocks, and wherein the first engagement structure comprisesthe first occlusal block and the third engagement structure comprisesthe second occlusal block.

Clause 73. The apparatus of clause 72, further comprising a thirdocclusal block corresponding to the first occlusal block and a fourthocclusal block corresponding the second occlusal block and wherein thesecond engagement structure comprises the third occlusal block and thefourth engagement structure comprises the fourth occlusal block.

Clause 74. The apparatus of clause 71, wherein the first engagementsurface is inclined relative to a midline of the first engagementstructure and the second engagement surface is opposingly inclinedrelative to a midline of the second engagement structure to limit thelateral movement of the mandible and reposition the mandible.

Clause 75. The apparatus of clause 71, wherein the third engagementsurface is inclined relative to a midline of the third engagementstructure and the fourth engagement surface is opposingly inclinedrelative to a midline of the fourth engagement structure to limitlateral movement of the mandible and reposition the mandible.

Clause 76. A plurality of occlusal blocks for a mandibular relocation,comprising: a first occlusal block comprising a first engagement surfaceand a first side surface; a first undercut formed in the first sidesurface of the first occlusal block; a first keyway formed in the firstside surface of the first occlusal block; a second occlusal blockcomprising a second engagement surface to engage the first engagementsurface and a second side surface; and a second keyway formed in thesecond side surface of the second occlusal block.

Clause 77. The plurality of occlusal blocks of clause 76, wherein thefirst side surface has a lower portion and an upper portion.

Clause 78. The plurality of occlusal blocks of clause 77, wherein thelower portion extends from a base towards an occlusal surface.

Clause 79. The plurality of occlusal blocks of clause 78, wherein theupper portion extends from the occlusal surface towards the base.

Clause 80. The plurality of occlusal blocks of clause 79, wherein theupper portion meets the lower portion along a mesial-distal line betweenthe occlusal surface and the base.

Clause 81. The plurality of occlusal blocks of clause 80, the first sidesurface of the lower portion forms the undercut by extending from thebase towards the upper portion at a draft angle with respect to a lineperpendicular to the occlusal plane.

Clause 82. The plurality of occlusal blocks of clause 81, wherein thefirst side surface is a buccal side surface and the first occlusal blockincludes a lingual side surface, opposite the buccal side surface, thelingual side surface extending from the base at the draft angle.

Clause 83. The plurality of occlusal blocks of clause 82, wherein thedraft angle is between 1 degree and 45 degrees.

Clause 84. The plurality of occlusal blocks of clause 82, wherein thedraft angle is about 5 degrees.

Clause 85. A system comprising: a plurality of first and secondorthodontic aligners for a plurality of stages of treatment, each of theplurality of first and second orthodontic aligners having: toothreceiving cavities for incrementally repositioning a patient's teethfrom an initial position towards a final position; the plurality offirst orthodontic aligners having: a first occlusal block comprising afirst engagement surface and a first side surface; a first undercutformed in the first side surface of the first occlusal block; a firstkeyway formed in the first side surface of the first occlusal block; theplurality of second orthodontic aligners having: a second occlusal blockcomprising a second engagement surface to engage the first engagementsurface and a second side surface; and a second keyway formed in thesecond side surface of the second occlusal block.

Clause 86. The plurality of occlusal blocks of clause 85, wherein thefirst side surface has a lower portion and an upper portion.

Clause 87. The plurality of occlusal blocks of clause 86, wherein thelower portion extends from a base towards an occlusal surface.

Clause 88. The plurality of occlusal blocks of clause 87, wherein theupper portion extends from the occlusal surface towards the base.

Clause 89. The plurality of occlusal blocks of clause 88, wherein theupper portion meets the lower portion along a mesial-distal line betweenthe occlusal surface and the base.

Clause 90. The plurality of occlusal blocks of clause 89, the first sidesurface of the lower portion forms the undercut by extending from thebase towards the upper portion at a draft angle with respect to a lineperpendicular to the occlusal plane.

Clause 91. A system comprising: a plurality of first and secondorthodontic aligners for a plurality of stages of treatment, each of theplurality of first and second orthodontic aligners having: toothreceiving cavities for incrementally repositioning a patient's teethfrom an initial position towards a final position; the plurality offirst orthodontic aligners having: any combination of the occlusalblocks of clauses 1-91.

Embodiments of the present disclosure have been shown and described asset forth herein and are provided by way of example only. One ofordinary skill in the art will recognize numerous adaptations, changes,variations and substitutions without departing from the scope of thepresent disclosure. Several alternatives and combinations of theembodiments disclosed herein may be utilized without departing from thescope of the present disclosure and the inventions disclosed herein.Therefore, the scope of the presently disclosed inventions shall bedefined solely by the scope of the appended claims and the equivalentsthereof.

What is claimed is:
 1. A plurality of occlusal blocks for a mandibular relocation, comprising: a first occlusal block comprising a first engagement surface and a first side surface; a first undercut formed in the first side surface of the first occlusal block; a second occlusal block comprising a second engagement surface to engage the first engagement surface and a second side surface; and a second undercut formed in the second side surface of the second occlusal block.
 2. The plurality of occlusal blocks of claim 1, the undercut extending from a base of the first occlusal block towards an occlusal surface of the first occlusal block at a draft angle with respect to a line perpendicular to the occlusal plane.
 3. The plurality of occlusal blocks of claim 2, wherein the first side surface is a buccal side surface and the first occlusal block includes a lingual side surface, opposite the buccal side surface, the lingual side surface including a third undercut.
 4. The plurality of occlusal blocks of claim 2, wherein the draft angle is between about 1 degree and about 45 degrees.
 5. The plurality of occlusal blocks of claim 2, wherein the draft angle is about 25 degrees.
 6. A plurality of occlusal blocks for a mandibular relocation, comprising: a first occlusal block comprising a first engagement surface and a first side surface; a first undercut formed in the first side surface of the first occlusal block; a first keyway formed in the first side surface of the first occlusal block; a second occlusal block comprising a second engagement surface to engage the first engagement surface and a second side surface; and a second keyway formed in the second side surface of the second occlusal block.
 7. The plurality of occlusal blocks of claim 6, wherein the first side surface has a lower portion and an upper portion.
 8. The plurality of occlusal blocks of claim 7, wherein the lower portion extends from a base towards an occlusal surface.
 9. The plurality of occlusal blocks of claim 8, wherein the upper portion extends from the occlusal surface towards the base.
 10. The plurality of occlusal blocks of claim 9, wherein the upper portion meets the lower portion along a mesial-distal line between the occlusal surface and the base.
 11. The plurality of occlusal blocks of claim 10, the first side surface of the lower portion forms the undercut by extending from the base towards the upper portion at a draft angle with respect to a line perpendicular to the occlusal plane.
 12. The plurality of occlusal blocks of claim 11, wherein the first side surface is a buccal side surface and the first occlusal block includes a lingual side surface, opposite the buccal side surface, the lingual side surface extending from the base at the draft angle.
 13. The plurality of occlusal blocks of claim 12, wherein the draft angle is between 1 degree and 45 degrees.
 14. The plurality of occlusal blocks of claim 12, wherein the draft angle is about 5 degrees.
 15. A system comprising: a plurality of first and second orthodontic aligners for a plurality of stages of treatment, each of the plurality of first and second orthodontic aligners having: tooth receiving cavities for incrementally repositioning a patient's teeth from an initial position towards a final position; the plurality of first orthodontic aligners having: a first occlusal block comprising a first engagement surface and a first side surface; a first undercut formed in the first side surface of the first occlusal block; a first keyway formed in the first side surface of the first occlusal block; the plurality of second orthodontic aligners having: a second occlusal block comprising a second engagement surface to engage the first engagement surface and a second side surface; and a second keyway formed in the second side surface of the second occlusal block.
 16. The plurality of occlusal blocks of claim 15, wherein the first side surface has a lower portion and an upper portion.
 17. The plurality of occlusal blocks of claim 16, wherein the lower portion extends from a base towards an occlusal surface.
 18. The plurality of occlusal blocks of claim 17, wherein the upper portion extends from the occlusal surface towards the base.
 19. The plurality of occlusal blocks of claim 18, wherein the upper portion meets the lower portion along a mesial-distal line between the occlusal surface and the base.
 20. The plurality of occlusal blocks of claim 19, the first side surface of the lower portion forms the undercut by extending from the base towards the upper portion at a draft angle with respect to a line perpendicular to the occlusal plane. 